Regenerable method and system for desulfurizing reformate

Abstract

A system for removing sulfur from a continuous reformate stream feeding a fuel cell stack. First and second sulfur traps are disposed in parallel between a hydrocarbon reformer and the fuel cell stack. The ends of the sulfur traps are connected to conventional four-way valves such that either trap may be selected for trapping sulfur from the reformate stream, while the other trap is undergoing regeneration by backflushing the accumulated adsorbed sulfur deposits. Thus, the sulfur traps may be used and stripped alternately, permitting continuous supply of desulfurized reformate to the fuel cell assembly. In a currently preferred embodiment, the hot cathode air exhaust is used to assist in stripping the out-of-service trap. In an alternative embodiment, two reformers are provided and the reformers are alternately regenerated along with their respective traps.

1. A fuel cell system comprising:
 a) a fuel cell stack; 
 b) a first catalytic hydrocarbon reformer for reforming a hydrocarbon fuel and thereby generating a stream of reformate for use in said fuel cell stack; 
 c) first and second sulfur traps disposed in parallel flow downstream of said reformer for desulfurizing said stream of reformate; 
 d) first and second selector valves fluidly coupled to said first and second sulfur traps for selecting between alternate flow paths therethrough for said reformate stream, said first selector valve being disposed in series flow with said reformate stream upstream of said first and second sulfur traps and said second selector valve being disposed in series flow with said reformate stream downstream of said first and second sulfur traps, and 
 e) a second catalytic hydrocarbon reformer disposed in parallel with said first catalytic hydrocarbon reformer, 
 wherein said first and second selector valves are configured such that when either one of said first and second sulfur traps is fluidly coupled to receive said reformate stream the other one of said first and second sulfur traps is fluidly coupled to receive a regenerating gas, 
 wherein said second selector valve includes a backflush inlet configured to receive a stream of said regenerating gas and is disposed in said regenerating gas stream upstream of said other one of said first and second sulfur traps that is fluidly coupled to receive said regenerating gas, 
 wherein said second selector valve is configured to provide a continuous stream of desulfurized reformate to said fuel cell stack, 
 wherein said first sulfur trap is fluidly coupled to said first reformer and said second sulfur trap is fluidly coupled to said second catalytic hydrocarbon reformer, 
 wherein said first selector valve is disposed upstream of and in flow connection with said first and second reformers such that each reformer is regenerated along with its respective trap, and 
 wherein said fuel cell stack further produces a flow of spent anode gas and further including a third selector valve fluidly coupled upstream to said first and second catalytic hydrocarbon reformers for selecting between alternate flow paths therethrough for at least a portion of said spent anode gas.